1. Field of the Invention
The present invention relates generally to a long range eye-safe laser radar (LADAR) system for use in an environment where real-time non-cooperative identification of an object is required. In particular, a laser beam is aimed at an object, the laser energy reflected from the object is collected by a detector array for use in generating a composite of both a high resolution 3-Dimensional (3D) shape of the object and the object's high resolution micro-Doppler vibration spectrum, a characteristic of the object as unique as a fingerprint. The composite is then used to automatically identify the object by comparison to a database of similar composite sets of 3D shape and vibration spectrum information with the results of the identification conveyed to the user.
2. Description of the Prior Art
LADAR systems are used in a wide variety of military and civilian applications. Common uses of LADAR systems are determining the range of objects, determining the velocity of moving objects and the capturing of 3D characteristics of objects. The use of LADAR systems to aid civilian law enforcement and the military in the non-cooperative identification of subjects and objects is well under way. LADAR systems for use in automatic target identification have been investigated by the United States Department of Defense's Automatic Target Recognition Working Group. The current state of the art will produce high reliability target ID based on 3-D shape information derived from 25 pixels per square meter of target with range accuracies of a few inches and acceptably low false alarm rates. However, 3D LADAR lacks the ability to discern the object's micro-Doppler vibration spectrum. Recently, the Research Institute for Optronics and Pattern Recognition under the direction of the German Defense Research Establishment has demonstrated the potential for object identification using spatially resolved micro-Doppler imaging, but the design lacked the ability to develop simultaneous 3D image information. Characterization of an object's vibration spectrum using micro-Doppler analysis is well underway and is the subject of numerous inventions and papers. Eye-safe LADAR systems are the subject of a wide variety of implementations and have been demonstrated by many foreign and domestic entities.
Current eye-safe LADAR systems do not provide the capability to simultaneously collect, on a single focal plane array in real-time, both the coherent laser energy necessary for high spatially resolved micro-Doppler imagery and the incoherent laser energy for high range resolution necessary to generate 3D images. Also lacking in current LADAR systems is the capability to perform signal processing sufficient to create a micro-Doppler signature and 3D image composite that is unique to each object. Making the signature and image composite available for comparison to a database of known signature and image composites can lead to the automatic non-cooperative identification of an object, a feature not available in current LADAR systems. Automatic real-time non-cooperative identification of an object is a long sought capability for both civilian and military organizations. The present invention, a Combined Coherent and Incoherent Imaging LADAR, corrects deficiencies existing in the current state of the art.